JavaScript Resources

Sites

JavaScript at internet.com - Excellent site for JavaScript, contains lots of free JavaScript under numerous categories with a neat interface, explanation and demo. A must visit site for any JavaScript enthusiast. You can study the JavaScripts there and could come up with your very own script giving you the solution, this is how I prefer it (I have to write it on my own, with my own variables); but of course you can copy-paste them too!
Netscape's JavaScript - One of the most authoritative source of information on JavaScript. Contains exhaustive documentation on core JavaScript, Client Side JavaScript, Server Side JavaScript, references, guides... - in a nutshell, a haven of information on JavaScript. Another important link on the same site is - http://developer.netscape.com/docs/manuals/js/. You simply can not do good programming in JavaScript without visiting this site time and again.
JScript at MSDN - Microsoft's version of JavaScript. You'll need to know both for cross browser programming.
JavaScript at Faqts - Very, very good resource for JavaScript code, information, documentation & of course FAQs. The solution given is comprehensive and explanation is really neat. Maintained by Martin Honnen and updated relentlessly.
JavaScript World - Another site for lots of scripts and references.
Web Monkey - Another good site for web related information. Contains a good information about DHTML, CSS as well.
Web Developer's JavaScript - For tips and tricks on JavaScript, besides HTML, DHTML, CSS etc.

Books

JavaScript Programmer's Reference - This big book from Wrox press is a very good reference for JavaScript programming.	Beginning Javascript - Another good book from Wrox press to start JavaScript programming. Definitely, not only for beginners.
Javascript : The Definitive Guide - Despite of being such a fast changing language, this huge book (some odd 1000+ pages) manages to provide very useful and comprehensive guide for JavaScript, providing cross browser code in most cases.	Online resources/documentations are the best ones for JavaScript, as they provide the latest information about the language which changes so fast and with all those cross browser compatibility issues.

News Groups

I believe, news groups prove very useful when you get stuck in a particular problem and need solution immediately, when you don't want to go through all those documentations to find what's missing, at times even though you have all the docs you just don't know what exactly applies to YOUR problem; news groups help you to find solution to your problem almost immediately with so many experts around the world voluntarily helping you with your specific problem.
Here are some JavaScript news groups -

comp.lang.javascript - The basic JavaScript usenet news group. You can also see it archived at groups.google.com.
microsoft.public.scripting.jscript - Microsoft's news group for their JScript (both client side and server side). Frequented by many Microsoft MVPs and other experts. (News Server - msnews.microsoft.com).
netscape.devs-javascript - Netscape's news group for JavaScript. Another one frequented by experts of the subject. (News Server - secnews.netscape.com).